When I was researching to write my blogpost about vtables:
https://peter0x44.github.io/posts/vtables-itanium-abi/
I noticed a few improvements I could make to -fdump-lang-class's output
-fdump-lang-class prepended "0x" to HOST_WIDE_INT_PRINT_HEX outputs, but the
macro already includes that prefix, producing "0x0x..." in dumps.
Some vtable entries hold signed values e.g. vcall offsets, vbase offsets,
offset-to-top. When expr_as_string prints those INTEGER_CSTs,
negative offsets appear as large (unsigned) values. Print integer vtable
entries as signed values, and keep expr_as_string for all other entries.
gcc/cp/ChangeLog:
* class.cc (dump_vtable_entry): New function.
(dump_array): Use it.
(dump_class_hierarchy_r): Drop redundant literal 0x from
HOST_WIDE_INT_PRINT_HEX formatting.
(dump_vtable): Likewise.
---
gcc/cp/class.cc | 31 ++++++++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)
diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc
index 6e4dc3cb093..2ea90f6f8bf 100644
--- a/gcc/cp/class.cc
+++ b/gcc/cp/class.cc
@@ -167,6 +167,7 @@ static int maybe_indent_hierarchy (FILE *, int, int);
static tree dump_class_hierarchy_r (FILE *, dump_flags_t, tree, tree, int);
static void dump_class_hierarchy (tree);
static void dump_class_hierarchy_1 (FILE *, dump_flags_t, tree);
+static void dump_vtable_entry (FILE *, tree);
static void dump_array (FILE *, tree);
static void dump_vtable (tree, tree, tree);
static void dump_vtt (tree, tree);
@@ -9762,7 +9763,7 @@ dump_class_hierarchy_r (FILE *stream,
tree base_binfo;
int i;
- fprintf (stream, "%s (0x" HOST_WIDE_INT_PRINT_HEX ") ",
+ fprintf (stream, "%s (" HOST_WIDE_INT_PRINT_HEX ") ",
type_as_string (BINFO_TYPE (binfo), TFF_PLAIN_IDENTIFIER),
(HOST_WIDE_INT) (uintptr_t) binfo);
if (binfo != igo)
@@ -9785,7 +9786,7 @@ dump_class_hierarchy_r (FILE *stream,
if (BINFO_PRIMARY_P (binfo))
{
indented = maybe_indent_hierarchy (stream, indent + 3, indented);
- fprintf (stream, " primary-for %s (0x" HOST_WIDE_INT_PRINT_HEX ")",
+ fprintf (stream, " primary-for %s (" HOST_WIDE_INT_PRINT_HEX ")",
type_as_string (BINFO_TYPE (BINFO_INHERITANCE_CHAIN (binfo)),
TFF_PLAIN_IDENTIFIER),
(HOST_WIDE_INT) (uintptr_t) BINFO_INHERITANCE_CHAIN (binfo));
@@ -9878,6 +9879,23 @@ dump_class_hierarchy (tree t)
}
}
+/* Dump VALUE, a vtable entry, to STREAM. Print integer offsets as signed
+ values. */
+
+static void
+dump_vtable_entry (FILE *stream, tree value)
+{
+ /* Vtable offset entries are stored in the pointer-sized vtable entry
+ type, but should be displayed as signed ptrdiff_t values. */
+ tree cst = value;
+ STRIP_NOPS (cst);
+
+ if (TREE_CODE (cst) == INTEGER_CST)
+ print_decs (wi::to_wide (cst), stream);
+ else
+ fprintf (stream, "%s", expr_as_string (value, TFF_PLAIN_IDENTIFIER));
+}
+
static void
dump_array (FILE * stream, tree decl)
{
@@ -9896,8 +9914,11 @@ dump_array (FILE * stream, tree decl)
FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (DECL_INITIAL (decl)),
ix, value)
- fprintf (stream, "%-4ld %s\n", (long)(ix * elt),
- expr_as_string (value, TFF_PLAIN_IDENTIFIER));
+ {
+ fprintf (stream, "%-4ld ", (long)(ix * elt));
+ dump_vtable_entry (stream, value);
+ fprintf (stream, "\n");
+ }
}
static void
@@ -9919,7 +9940,7 @@ dump_vtable (tree t, tree binfo, tree vtable)
if (ctor_vtbl_p)
{
if (!BINFO_VIRTUAL_P (binfo))
- fprintf (stream, " (0x" HOST_WIDE_INT_PRINT_HEX " instance)",
+ fprintf (stream, " (" HOST_WIDE_INT_PRINT_HEX " instance)",
(HOST_WIDE_INT) (uintptr_t) binfo);
fprintf (stream, " in %s", type_as_string (t, TFF_PLAIN_IDENTIFIER));
}
--
2.54.0
